The Growing Threat of Chronic Wasting Disease – What Hunters Need to Know

The Growing Threat of Chronic Wasting Disease: What Hunters Need to Know

By Catherine Cummings

As the cooler weather settles in and the days shorten, Iowa hunters gear up for one of the most anticipated events of the deer season: gun season. While excitement builds for the season, there’s a pressing issue that no hunter should ignore–chronic wasting disease (CWD). As continues to spread across Iowa, it poses serious challenges for the deer population, hunters, and broader conservation efforts.

The Iowa Department of Natural Resources (DNR) has monitored for CWD since 2002, with the first wild detection in Allamakee County in 2013. As of September 2024, CWD has been detected in 23 Iowa counties (scan the QR code for the most up-to-date data on the DNR’s CWD Interactive Dashboard).

With gun season offering a prime opportunity to contribute to the Iowa DNR’s monitoring efforts, hunters are at the front lines of helping monitor and manage this disease. Understanding what CWD is, how the disease is spread, and what steps hunters can take to help mitigate its effects has never been more important as we enter the heart of hunting season.

What is Chronic Wasting Disease?

Chronic wasting disease, otherwise known as CWD, is a 100% fatal infectious disease of cervids that has been detected in captive or wild populations of deer, elk, moose, and caribou in the United States, Canada, Norway, Finland, Sweden, and South Korea. The disease is caused by the misfolding of naturally occurring proteins, called prions. Misfolded infectious prions can be found throughout the entire body of a cervid (including muscle tissue), but areas such as the brain, spinal cord, and lymph nodes contain high concentrations of prions. As the disease progresses to the clinical stage, prions accumulate in the brain, causing plaques or “holes” in the brain, resulting in behavioral changes and eventually death.

The Silent Spread: Incubation Period and Transmission

One of the challenges associated with CWD monitoring and management is the length of its incubation period. After an animal is infected, it can take between 18 to 36 months (1.5 to 3 years) before it shows any outward signs of the disease. During the incubation period, infected animals begin shedding prions through bodily fluids such as saliva, urine, blood, and feces, spreading the disease while appearing perfectly healthy. This silent spread makes CWD particularly challenging to detect and manage, as infected deer that look healthy are able to spread the disease through direct contact with healthy deer (deer-to-deer contact) or through the spread of prions in the environment (environmental transmission). Thus, CWD is impossible to diagnose “on the hoof”–currently the only way to confirm that a deer has CWD is through diagnostic testing.

Once the incubation period ends, infected deer enter the “clinical” stage, quickly showing signs such as weight loss, lack of coordination, excessive salivation, and increased thirst or urination. Behavioral changes like disorientation, isolation, and losing fear of humans may also appear.

How Does Iowa DNR Manage CWD?

The Iowa DNR is committed to a deer management strategy that supports quality deer hunting while minimizing negative impacts such as property/crop damage and disease. Since overabundant deer populations likely increase the rate of CWD transmission, keeping deer densities at a healthy level is important. This means that in some CWD-positive counties increasing doe harvest is the responsible action–but not always. Many Iowa counties are currently on the low end of their deer management objective, in which case encouraging more doe harvest may not be necessary. The DNR does not employ sharpshooters to manage our county deer populations, but instead relies solely on hunters for harvest-based management.

Testing for CWD in Iowa

The Iowa DNR relies primarily on the submission of hunter-harvested and road-killed deer to track the spread and prevalence of CWD in the state. Hunter-harvested samples are voluntary submissions in Iowa and a majority of the samples are collected during the firearm seasons (also known as Shotgun 1 and Shotgun 2 seasons). The medial retropharyngeal lymph nodes are collected from harvested deer, which requires a cut behind the jaw. If you are planning to mount your deer, we will work with your taxidermist to collect the sample.

In Iowa hunters have two options for sample submission:

DNR Surveillance Program: To provide a sample for the DNR Surveillance Program, please contact your local DNR wildlife staff. Additionally there are freezers across Iowa where hunters can drop deer heads off at any time for sample submission. This method is free for hunters who participate until the quota in the county or Deer Management Zone is reached. You can monitor progress towards county surveillance goals on our Interactive CWD Dashboard.
Hunter Submission Pathway: For those seeking expedited results (i.e., results with a faster turnaround time than the DNR surveillance program) or for deer that are not eligible for the DNR Surveillance Program (fawns), hunters can pay a $25 fee to have samples tested through the Iowa State University Veterinary Diagnostic Laboratory. DNR wildlife staff can pull samples for hunters participating in the Hunter Submission Pathway.

Providing samples to either the DNR Surveillance Program or the Hunter Submission Pathway helps the Iowa DNR understand the spread and prevalence of CWD. Additionally, results of the diagnostic testing can help you make informed decisions about consuming venison. Although current evidence supports the presence of a strong species barrier mitigating the risk of CWD transmitting to humans, the Centers for Disease Control and Prevention (CDC) advise to test deer harvested in areas where the disease has been detected and for individuals to not consume meat from CWD-positive animals.

What Hunters Can Do to Combat CWD in Iowa

Hunters are at the forefront of CWD management. By continuing to harvest deer, especially in areas where CWD has been detected, hunters help manage deer densities and reduce the risk of disease transmission. There are some additional practices hunters can partake in to help protect the state’s deer population and preserve our hunting heritage. Here are some best practices hunters can consider:

Know the CWD Status of the County You Hunt: You can track CWD detections in each county via the Interactive CWD Dashboard.
Proper Carcass Disposal: To help reduce the risk of spreading CWD, hunters are encouraged to not transport carcasses away from the harvest site if possible. If transport away from the harvest site is needed, proper disposal of carcasses is very important. Hunters may take them to a landfill that accepts deer carcasses. This minimizes the chance of contaminating new areas with infected prions.
Avoid Baiting and Feeding Deer: Hunters should avoid using bait or mineral licks, which attract deer to one location, increasing the risk of disease transmission. While natural congregation will always occur due to licking branches, scapes, etc., artificial congregation at bait or mineral sites has high transmission potential and can easily be avoided. If you plan to remove attractants off the landscape, long term mitigation requires removing the contaminated soil to eliminate prions from the environment.
Become a CWD Ambassador: The Iowa DNR, in collaboration with Iowa State University Extension and Outreach, offers the Chronic Wasting Disease Ambassadors Program. This program educates hunters, landowners, and local leaders about the management, prevention, and testing for CWD. Additionally ambassadors learn key communication skills and are provided resources to help educate others within their communities. Please track where CWD Ambassador classes are offered here.

Conclusion

As we head into Iowa’s Gun Season, it’s important to keep CWD in mind and to take steps to protect our deer herds and hunting heritage. Your efforts–whether through sample submission, knowing the CWD status where you hunt, proper carcass disposal, avoiding artificial congregation, or becoming a CWD ambassador–make a significant impact in managing CWD across Iowa. Your role as a hunter is vital in preserving Iowa’s wildlife for future generations. Good luck this season, and remember if you have any questions about CWD or deer diseases, feel free to reach out to me at catherine.cummings@dnr.iowa.gov or 319-480-7829.